Safety and Diagnostic Yield of Kidney Transplant Biopsies in an Interventional Nephrology Program: A Retrospective Single-Center Study

Background: Kidney transplant (KT) biopsy remains the gold standard in diagnosing rejection. However, biopsy carries risk of complications which must be weighed against the diagnostic yield, and variability exists between providers and centers in aggressiveness of pursuing transplant biopsy. We created a renal biopsy registry at our center for both research and quality improvement purposes. We reviewed all transplant biopsies performed to determine the rate of complications and diagnostic yield. Methods: We performed a retrospective chart review of all KT biopsies performed by our Interventional Nephrology program between 11/27/2017 and 4/9/2024. Data collected included pathological diagnosis and complications. Major bleeding was defined as the need for secondary interventional procedure, need for blood transfusion, need for surgery, hospitalization, hematoma >5 cm, or death. Minor bleeding was defined as hemoglobin drop of >1.5 g/dL, hematoma <5 cm, or uncomplicated gross hematuria. Diagnoses of rejection included all forms of rejection, including borderline cases. Results: A total of 282 biopsies were performed, of which 154 (54.6%) were KT biopsies. Major bleeding events occurred in 3 KT patients (1.95%). All 3 patients presented with gross hematuria. The first patient was found to have an arteriovenous fistula and died of an unrelated cardiac event before planned IR embolization. The second patient developed urinary obstruction secondary to bleeding and required a nephrostomy tube for 51 days. The third patient required 1 unit of blood and was observed in the hospital until the hematuria resolved. Minor bleeding occurred in 2 additional patients (1.3%), manifest in both as hemoglobin drop >1.5 g/dL. Of the KT biopsies, 65/154 (42%) revealed evidence of rejection. Conclusion: In our center, major bleeding after KT biopsy was uncommon relative to the frequency of transplant rejection diagnoses. Our findings support the consideration of an aggressive approach to KT biopsy for detection of rejection. Further analyses of our registry are planned to determine factors most likely associated with rejection (e.g., donor-specific antibodies, time since transplant, cell-free DNA levels) to improve the screening process for biopsy referral and help personalize the decision-making process for individual patients.